Brake with field responsive material

ABSTRACT

A controllable brake includes a rotor supported on one shaft end. The rotor is housed within a chamber containing a field controllable material which is acted upon by a magnetic field generator to change the rheology of the material and thereby impede movement of the rotor. The shaft is supported by two bearings which, in combination with the housing define a second housing chamber adapted to enclose means for monitoring and/or controlling the brake and in this way, an integrated, compact controllable brake is provided.

FIELD OF THE INVENTION

The invention relates to the area of brakes, clutches, resistancegenerating devices and motion control devices. Specifically theinvention relates to devices employing a field responsive material forcontrolling torque in rotary acting devices or linearly-acting devices.

BACKGROUND OF THE INVENTION

Devices employing a field responsive material for damping andcontrolling vibration and shock are known. Such a field responsivematerial may comprise a suitable magnetorheological (MR) material wellknown to one skilled in the art. As the description proceeds, the fieldresponsive material may be referred to as either “MR medium” or “MRmaterial” or “field responsive material” or “field controllablematerial”. Additionally, for purposes of clarity throughout thisdisclosure, devices employing such a field controllable material willgenerally be referred to as either “magnetorheological devices” or “MRdevices” or “field controllable devices” or “field responsive devices”.MR devices may be of the “rotary-acting” or “linear-acting” variety, andcan provide variable controlled torques or forces. Known MR devices mayinclude for example rotary brakes, rotary clutches and linear dampers.

Field controllable devices typically include a housing or chamber thatcontains a quantity of a magnetically controllable material, and amoveable member, such as a piston or rotor mounted for movement throughthe material in the housing. A magnetic field generator (a coil orpermanent magnet) produces a magnetic field through one or more polepieces for directing a magnetic flux through desired regions of thecontrollable material.

The field controllable material employed in MR devices is comprised ofsoft-magnetic or magnetizable particles dispersed within a carrier,frequently a liquid. While many current applications employ a liquidcarrier, it also will be appreciated that the carrier may also comprisegaseous dispersions, for example as a powder. However the requiredcarrier is dependent on the specific application for the MR device.Typical particles include carbonyl iron or stainless steel, and thelike, having various shapes, but which are preferably spherical and havemean diameters of between about 0.1 μm to about 500 μm. The carriermaterials may include hydraulic oils for example.

In operation, the field controllable material exhibits a rheologychange, i.e., an increase in viscosity or resistance to shear, uponbeing exposed to a magnetic field. The greater the magnitude of themagnetic field passing through the field controllable material, thehigher the shear stress or torque that can be achieved by the MR device.Such MR materials are readily commercially available in variousformulations from Lord Corporation of Cary, N.C., and the selection ofthe particular MR material is typically determined by the desiredapplication for the MR device.

MR devices, in particular MR brakes, are used whenever it is necessaryto control motion, and in applications where it is desirable to controlthe velocity or energy dissipation in a dynamic system. This includessystems irrespective of whether the systems are driven by pneumatics,manually by an operator or by another motive force generating means. Thespecific application is controllable energy dissipation, in the rotarysense. Energy is removed from a dynamic system to give position and/orvelocity control, or to generate a desired resistance torque.

Examples of such systems include drive-by-wire systems such as might beapplied in a vehicle, fork lift, or the like. In such applications, itis desirable to maintain the function of traditional mechanical controlsin a system controlled in a different manner. For example, a steeringwheel may be used which implements a magnetic brake, but through the useof electronics provides signals to a motor such as a servo motor, toactuate the device to be controlled, such as steered wheels, flightcontrol surfaces, etc. Depending on the position of the device as movedby the servo motors, it may be desirable to provide tactile feedback tothe operator. Thus, when turning a wheel which incorporates an MR brake,position sensors and appropriate electronics may be implemented toprovide torque feedback by actuating the field generator in the magneticbrake to affect the MR material and increase resistance to motion by arotor in the brake. For example, such an application can be a steeringwheel, to which it is attached, as to maintain a realistic “feel” forthe operator, in a manner duplicating the tactile feedback of purelymechanical systems.

Often, the space allotted for the use of these devices is limited andspecific applications require that the devices be maintained as small aspossible, while still providing sufficient resistance to the controldevice. It would be desirable to provide a compact, integrated device toaccommodate space limitations in specific applications.

The foregoing illustrates design criteria known to exist in presentfield responsive devices. Thus it is apparent that it would beadvantageous to provide an alternative directed to providing a fieldresponsive device that addresses one or more of the criteria associatedwith present devices. Accordingly, a suitable alternative is providedincluding features more fully disclosed hereinafter.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a controllable brake includes arotor having first and second rotor surfaces, an outer periphery and atleast one working portion proximate to or at the outer periphery. Ashaft has the rotor connected at one end of the shaft in a manner torestrain relative rotation therebetween. A housing includes a firstchamber housing the rotor therein in a manner to allow rotation thereof(rotatably housing), and including a magnetic field generator spacedfrom the rotor, and configured and positioned for conveying a magneticflux extending through controllable material between the field generatorand working portion, in a direction toward the at least one workingportion of the rotor. The controllable material is contained within thefirst chamber in contact with the at least one working portion of therotor. Electronics are provided for controlling and/or monitoringoperation of the brake. Such electronics may include sensors, poweramplifiers, signal conditioners, analog or digital circuitry employingcontrol algorithms, communications circuitry, as well as other likecircuitry and/or optical, magnetic and like components as will bereadily apparent to those of ordinary skill in the art. Morespecifically, the shaft may be supported by at least two bearings spacedfrom each other. The bearings are mounted on the housing in a manner todefine a second housing chamber. The control electronics are housed inthe second chamber. Typically, the second chamber is adjacent the firstchamber.

For purposes of the description of the preferred embodiments of theinvention, the term “working portion” refers to the portion of the rotorwhich, upon the application of a magnetic field, is engaged by the MRmedium to impede movement of the rotor.

In another aspect of the invention, a controllable MR brake includes arotor comprising first and second rotor surfaces, an outer periphery,and a working portion on at least one of the first and second rotorsurfaces at a position proximate to the outer periphery. The rotor isfixed to a shaft at one shaft end and the rotor and the shaft arerotatable together. A housing includes a first chamber rotatably housingthe rotor therein, and including a magnetic field generator spaced fromthe rotor and configured and positioned for conveying a magnetic fluxacting on a volume of controllable material located in the first housingchamber in contact with at least one surface proximate the outerperiphery. The controllable material is contained within the firstchamber to be in contact with at least the working portion of the rotor.Electronics serve to control and monitor operation of the brake. In amore specific aspect, a second chamber is included in the housing andhouses the electronics therein to provide a compact and integrated MRbrake with electronics housed therein.

The magnetic field generator may be an electromagnetic coil, with polespositioned for conveying a flux extending through the field controllablematerial at least on one side of the rotor, with the rotor configured asa disk. Alternatively, the magnetic field generator can be anelectromagnetic coil with poles positioned on both sides of the rotor onthe working surfaces thereof for conveying flux extending on both sides,with the rotor also being configured as a disk.

In specific applications, the shaft for the rotor is supported forrotation by two bearings in the housing, which allow for a secondchamber to house electronics, and seals are provided around the shaft atthe point of entry into the first chamber for sealing the first chamberto prevent the migration of the controllable material from the firstchamber to the second chamber.

In another more specific aspect of the invention, a return-to-centerdevice such as a torsional spring or like device may be provided to urgethe rotor to return to a relative center position.

Yet still further, the connection between the shaft and the rotor may bearranged so as to allow some backlash between the rotor and the shaft,and the control electronics can be arranged for detecting movement ofthe shaft and for causing the magnetic field generator to reducemagnetic field in response to the shaft movement to allow easy movementof the control device connected to the brake, such as a steering wheel,back from an end-of-movement position.

In an alternative configuration, the rotor can be configured to have aworking portion on the outer periphery and on the rotor surfaces at aportion proximate the outer periphery. The magnetic field generatorwhich is spaced from the rotor can be configured for conveying amagnetic flux extending through controllable material in directionsboth, (1) parallel to the shaft and perpendicular to the working portionproximate the outer periphery and (2) perpendicular to the shaft and tothe outer periphery of the rotor. This can be done by configuring, forexample, the magnetic field generator as an electromagnetic coil withone pole adjacent the working portion on one surface of the rotor, andthe other pole extending outside of the outer periphery, and at leastco-extensive with the outer periphery of the rotor.

In yet still a further aspect, the rotor can be configured as havingfirst and second rotor surfaces and an outer periphery. The outerperiphery is shaped such that the working portion of the rotor facesradially outward from the rotor and the shaft and has sufficient workingsurface as to allow a magnetic field to induce sufficient shear stresswithin the controllable material acting on the working surface toinhibit or prevent motion of the rotor. Such a rotor configuration caninclude a drum-like configuration in which the outer periphery is shapedfairly wide relative to the actual thickness of the rest of the rotor.In this manner, the magnetic field generator is configured to generate amagnetic field which acts on the controllable material adjacent and incontact with the working portion.

In such a configuration, the walls of the chamber in which the rotor ishoused can be tapered. The taper can be an amount sufficient to enhancemigration of field controllable material away from the shaft and towardthe working surface of the rotor. In addition, other alternativestructures can be built into the rotor proximate the shaft, the housing,and/or on the shaft itself as to create a tortuous path for the fieldcontrollable material, making it difficult to have it migrate towardsthe shaft and in the direction of seals associated with the shaft toretain the material within the chamber housing the rotor. The seals usedcan be conventional seals and/or of other configurations as will bereadily apparent to those of ordinary skill in the art, such as“v-seals” of conventional construction. Similarly, conventionalbearings, such as roller elements or bearings, can be used in supportingthe shafts as well as other types of bearings which are well known tothose of ordinary skill in the art, interchangeable therewith,including, without limitation, dry shaft bearings and the like.

The foregoing and other aspects will become apparent from the followingdetailed description of the invention when considered in conjunctionwith the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which form a part of this specification,illustrate several key embodiments of the present invention. Thedrawings and description together serve to fully explain the invention.

FIG. 1 is a longitudinal sectional view of a MR device having side coilsmounted therein, and having electronics integrated into the brake.

FIG. 2 is a longitudinal sectional view of an MR brake havingwrap-around poles for conveying magnetic flux which acts on workingsurfaces on the periphery of the rotor as well as on a side surfacethereof, and also including integrated electronics.

FIG. 3 is a longitudinal sectional view of a drum-style brake having themagnetic field generators positioned for acting on an enlarged outerperiphery making up a working surface of the rotor, and comprisingintegrated electronics within a second chamber and a torsionalreturn-to-center spring incorporated within the chamber housing therotor.

FIG. 4 is a longitudinal sectional view of a brake similar to that ofFIG. 1, but showing the magnetic field generator configured for actingon both surfaces of the rotor, and also showing integrated electronicsand how a return-to-center torsional spring can be incorporated withinthe housing for the electronics.

FIG. 5 is a longitudinal sectional view illustrating an alternativeconstruction of the brake of FIG. 3 showing tapered walls to enhancemigration of controllable material away from the shaft, and also showingalternative seal and bearing construction.

FIG. 6 is a cross-sectional view along line 6-6 of FIG. 5 illustratinghow a connection between a rotor and a shaft may be made and howbacklash between the rotor and the shaft may be allowed and implemented.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now turning to the Figures wherein like parts are referred to by thesame numbers in the several views, FIG. 1 illustrates a first embodimentof the present invention. The brake 11 illustrated in FIG. 1 is a sidecoil brake. As the description proceeds it should be understood thatalthough the term “brake” is used to describe the embodiments of theinvention the invention is generally a torque generating device thatcreates a dissipative torque in response to signals received orgenerated by the device 11. For purposes of describing the preferredembodiments of the invention the field controllable material isdisclosed as a free flowing material with particles randomly dispersedthroughout the carrier medium. However, it is contemplated that thefield controllable medium may also be comprised of a compacted materialwhere the particles are fixed relative to adjacent particles.

Brake 11 includes a housing 13 having a first chamber 15 which housesrotor 21 for rotation therein. Optionally, a second housing chamber 17is provided and the chamber may enclose any combination of controlelectronics and control devices comprising for example: sensors forobtaining the displacement or velocity of the rotor 21; an amplifier forincreasing the low current signal sent to the field generator 31;controls for communicating with a vehicle operator or a third partylocated away from the brake, and a communication means for facilitatingsuch external communication. Such control electronics and controldevices are represented schematically in FIG. 1 and are identified as25. The control electronics are used to monitor and/or control operationof device 11. The present invention brake permits control electronicsand devices to be located in the brake housing rather than at locationsexternal to the brake. This provides for a compact brake package and itis believed by locating the sensitive control electronics and controldevices internally, the electronics and devices are better protectedfrom dirt and particulate matter than with current devices which requirethe sensitive electronics to be located external of the device housing.As the description proceeds the components located in the second housingchamber may be described generally as “electronics” or “controlelectronics” for example, however it should be understood that this termshould not be limiting and the inventors do not wish to be limited toonly electronic type devices. Rather the term referring to the devicesand components housed in the second chamber shall more generally bedefined and comprised of any suitable means for controlling and ormonitoring operation of the device and such means may be comprised ofelectronic devices and/or mechanical components.

For purposes of describing the first embodiment of the invention, rotor21 is disk-shaped and is supported on a shaft 23 within the housing 13for rotation within the housing chamber 15. The rotor includes first andsecond surfaces and an outer periphery. The surfaces include workingportions near the outer periphery at regions on the surface of the rotorupon which the magnetic field acts. The working surface is identified at42 in FIG. 1. A typical magnetic flux line 37 associated with theapplied magnetic field is shown dashed in FIG. 1.

Brake housing 13 includes an open end where the first chamber 15 islocated and the open housing end and the chamber is closed and sealed byclosing plate 19. The first chamber also contains therein a volume offield controllable material 41 and electromagnetic field generators 29.The field generators comprise, for example, in one configuration, coil31 and pole piece 33. When activated, the magnetic field generator 29creates magnetic flux 37. In FIG. 1 the magnetic flux 37 is representedonly on one side of the rotor. However the magnetic field actstoroidally around the longitudinal shaft axis and along the entireworking surface 42 near the outer periphery of the rotor. The presenceof the magnetic field causes the field responsive material 41 to changeits rheology resulting in the development of a higher yield stress thatmust be exceeded to induce onset of shearing of the field responsivematerial. Typically, in the absence of a magnetic field, the particlesreturn to an unorganized or freely dispersed state and the apparentviscosity or shear flow resistance of the overall material 41 iscorrespondingly reduced. By activating the magnetic field, the material41 acts on the working portion 42 of the rotor 21 to inhibit itsrotational movement. The stippling that represents material 41schematically in FIG. 1 is shown in an organized manner in FIG. 1 andthe organized arrangement of the particles is a result of theapplication of field 37. As may be appreciated, supporting the shaft forrotation are bearings 35 which are shown as ball bearings, but may becomprised of any suitable bearing adapted to support rotation of shaft23.

To keep the field controllable material 41 within the first chamber 15,conventional seal 27 is provided to maintain the material 41 in chamber15 between plate 19 and pole piece 33. The seal may comprise anysuitable seal member adapted to prevent egress of the material from itsrequired location in chamber 15.

The monitoring and controlling electronics and devices 25 housed withinthe second chamber 17 may include multiple parts such as a rotating diskwhich is positionally detected by a sensor fixed within the walls of thechamber 17. The sensor may or may not be in contact with the rotatingshaft 23. Such a disk may be mounted along the shaft for example throughan intermediary sleeve 39.

In brake configuration 11, the magnetic flux 37 generated issubstantially perpendicular to surface 42 of the rotor 21, which in thisembodiment is shown as a disk, and the magnetic flux is substantiallyparallel to the shaft 23 as the flux passes through the fieldcontrollable material.

In the first embodiment of the invention illustrated in FIG. 1, the diskor rotor 21 is supported by shaft 23 at one shaft end. By supporting therotor 21 in this manner, a significant portion of the length of theshaft is available to effectively support other components and systemsof brake 11. The bearings 35 are located along the shaft length and arespaced apart by an axial distance required to provide rotor stability.As a result of such bearing location and alignment and location, achamber 17 is defined by the housing 13, bearings 35 and pole pieces 33wherein various sensors, electronics and other systems may be housed. Asa result, brake 11 represents a compact, integrated package generallycomprising the required mechanical rotor 21 and shaft 23, fieldresponsive material 41, field generator 29 and monitor and controlelectronics/sensors 25.

By locating the magnetic field generator 29 along one side of the rotor21, additional combinations of rotor 21 and field generator 29 may bestacked against the rotor 21 shown in FIG. 1. Any number of additionalrotors and field generators may be provided in order to provide theappropriate duplication of magnetic field generators 29 therebyresulting in a brake configuration with multiple disks, suitable for adesired application. Such a brake configuration having a plurality ofdisks and generators is not illustrated in FIG. 1. Such an alternateconfiguration would duplicate the FIG. 1 arrangement of rotor 21 andgenerator 29 in multiple iterations in the direction of end plate 19.Another advantage of first embodiment brake 11 is that by providing aplurality of rotors, the integrated package may be made smaller in theradial disk direction and thus may be more suitable for specificapplications where smaller brake configurations are required.

FIG. 2 illustrates a second embodiment of the present invention. Thesecond embodiment magnetic brake 51 is comprised of many of the elementscomprising brake 11 of FIG. 1. In this alternate embodiment, brake 51comprises housing 53 which defines chamber 55 for housing integratedelectronics/sensors 59 and also defines chamber 57 for housing rotor 71.Similar to the embodiment shown in FIG. 1, an end plate 19 is providedto close and seal the chamber 57. Although the plate is shown assubstantially planar, the plate may also comprise portions that extendsubstantially perpendicular to the plate and wrap around the housing.Ball bearings 67 serve to support the shaft 69 and conventional seal 87closes off the first chamber 57 to prevent the field responsive material85 from migrating from within the chamber 57 toward the bearings 67 andout of the chamber 57. In this alternate embodiment, the rotor 71 isattached to an end of shaft 69 is engaged to the rotor 71 and isrotatable with the shaft. The rotor is not limited to a disk-shapedconfiguration as will become more readily apparent from the discussionthat follows with reference to FIGS. 3 and 5.

As in the case with FIG. 1, a sleeve 65 can be mounted on the shaft 69and the monitoring and controlling electronics/sensor 59 are shownschematically in greater detail as made up, for example, of two parts 61and 63. A first part 61 may be fixed within the housing and not fixedlyengaged to the sleeve 65. The first part 61 can include monitor andcontrol electronics as well as sensors and/or detectors. Portion 63 canbe, for example, a rotating disk 52 mounted on the sleeve 65, therotation of which is detected by sensors mounted on the fixed part 61.Thus, the rotation of the shaft 69 and rotor 71 can be detected to allowappropriate control of electromagnetic field generator 73.

In the second embodiment brake 51, the electromagnetic field generator73 may include an electromagnetic coil 75 and a pole piece configurationthat is slightly different than the configuration of FIG. 1. Turning toFIG. 2, the pole configuration includes a first radially extending poleportion 77 and a second axially extending pole portion 79. The secondpole portion extends axially between radially extending pole portion 77and plate 19. Respective gaps 74 and 76 separate the outer periphery ofthe rotor 71 and the second pole portion 79 and the working surface 42and the first pole portion 77. When a current is supplied to the coil75, the field generator is activated and thereby generates magnetic flux81, represented dashed in FIG. 2, which acts on field responsivematerial that fills the chamber 57 and gaps 74 and 76. The field 81changes the rheology of the material causing the material to act uponthe rotor outer periphery and surface 42 and thereby provide resistanceto the motion of the rotor 71. Like brake 11 of FIG. 1, although asingle rotor 71/generator 73 combination is shown in FIG. 2, brake 51may comprise any suitable number of rotor/generator combinationsrequired to supply the requisite braking forces. The benefits associatedwith the first embodiment brake recited hereinabove are also realizedwith the second embodiment brake 51.

A third embodiment brake of the present invention is illustrated in FIG.3 and is referred to generally at 101. Brake 101 comprises hollow,cylindrical housing 103 which defines a first chamber 113 for housing arotor 107 for rotation therein about axis 99 and defines second chamber111 which houses monitoring and/or controlling electronics 115 in themanner previously described. The first chamber also houses a volume of afield responsive material 135. The rotor is a drum-shaped rotor thatcomprises a substantially I-shaped cross section with a wide outerannular peripheral portion 108 joined by a narrow web 112. The rotor 107is fixed in a conventional manner to one end of shaft 105 which in turnis supported by bearings 133 along the shaft length and generally in themanner previously described with first and second embodiment brakes 11and 51. Closing plate 109 serves to seal and close one end of thehousing 103. Plate 114 closes and seals the opposite housing end. Therotor may have any suitable cross section and other suitableconfigurations may comprise a C-shaped cross section and an L-shapedcross section for example.

The monitor and/or control electronics 115, in exemplary form, caninclude a combination of rotating disks having appropriate notches orother detectable indicia thereon. The rotating disks 117 may be mountedon a sleeve 118 fixed to shaft 105. Other components 119 of theelectronics 115 can be fixed within the chamber 111 in a manner so thatthe components surround the sleeve and are not in contact with thesleeve 118. In this way, the components 119 do not rotate with thesleeve 118. Sensors or brushes schematically represented at 121 may bemounted on member 119 to detect relative rotation of disk 117.

In the embodiment of FIG. 3, the seal 132 required to prevent migrationof material 135 from the first chamber 113 to the second chamber 111 isshown seated in bearing support plate 116. Such a suitable seal maycomprise the seal disclosed in the description of first and secondembodiment brakes. The suitable conventional seal may be supported inthe bearing support plate 116 or within bearings 133. An annular shroud120 is located between plates 114 and 116. Shroud 120, in combinationwith plates 114 and 116 encloses the sensing means 115 within chamber111.

Returning again to the rotor 107 of the third embodiment brake 101,rotor 107 is not substantially disk-shaped like disks 21 and 71previously described. As shown in FIG. 3, rotor enlarged peripheralportion 108 is located proximate electromagnetic coil 125 of fieldgenerator generally identified at 123. As shown by the stipplingrepresenting field responsive material 135, an annular gap 122 separatesthe portion 108 and field generator and the gap 122 is substantiallyfilled with a volume of the field controllable material 135. Themagnetic field produced by field generator 123 extends through material135 and the portion of the rotor identified at 108. The magnetic fieldis illustrated by magnetic field 129 represented as dashed in FIG. 3.

The magnetic field generator 123 generally comprises an electromagneticcoil 125 and pole pieces 127 which in combination generate anelectromagnetic flux represented by dashed field lines 129 which extendthrough the material 135 in a direction that is substantiallyperpendicular to shaft 105 and to the periphery of the rotor 107. Asshown in FIG. 3 the field generator is located radially outwardly fromthe rotor 107.

The third embodiment brake 101 comprises a return-to-center actingdevice, such as a torsion or torsional center-return spring 131 which ismounted within first housing chamber 113. Other center return devicesmay comprise bungee cords or other type elastic components. Generallythe suitable center return device is any device that stores energy asthe rotor and/or shaft are/is displaced from a center or start positionor orientation and then at a particular displacement releases the storedenergy to return the rotor and shaft to the start orientation. Theparticular displacement that results in a release of the stored energymay comprise for example, the operator releasing the shaft or rotor orthe shaft or rotor reaching a maximum angular displacement. The torsionreturn spring 131 typically assumes a torque free condition at thecenter position of a device with which brake 101 may be associated, suchas a steering wheel at the center position of the device. The return tocenter member is conventionally fixed at its ends to both the rotor 107,and end plate 109 so as to exert a progressively increasing returntorque to center position upon the turning of the device with which thebrake is associated, for example, a wheel. The return-to-center devicemay comprise a number of devices and attachment configurations.

FIG. 4 illustrates a fourth embodiment brake 201 similar to the firstembodiment brake 11. In the fourth embodiment brake, the brake housing203 includes a first chamber 215 wherein rotor 219 is located forrotation therein and the rotor is fixed to one end of shaft 209. Thechamber 215 includes a volume of a field responsive material 217therein. Conventional seal 213 seals the chamber 215 by preventing thefield controllable material from migrating out of the chamber 215. Plate207 closes the chamber 215 after the brake 201 is fully assembled.Bearings 211 support shaft 209 away from the shaft end supporting therotor 219. The housing 203 also defines a second chamber 205 for housingthe monitoring and control electronics and devices. The control means isrepresented schematically and referenced at 229 in FIG. 4. A torsionreturn spring 231 may be provided within the second chamber 205, fixedlysecured at the spring ends to an internal wall of the second chamber205, and to a sleeve 232 upon which portions of the control means 229may be also mounted for rotation therewith. The sleeve is made integralwith the shaft 209 for rotation therewith.

In the embodiment of the invention illustrated FIG. 4, the magneticfield generator 221 comprises an annular pole piece 225 having aU-shaped cross section and an electromagnetic coil 223 located withinthe open portion of the pole piece and radially outwardly from andadjacent to the outer periphery of the disk-shaped rotor 219. The polepiece 225 could be comprised of separate pole pieces for ease ofassembly and manufacture. As shown in FIG. 4, the legs or side portionsof the poles 225 a and 225 b extend toward the central longitudinal axisof rotation of shaft 209 and adjacent the rotor working surfaces 219 aand 219 b. Gaps separate the pole piece legs 225 a, 225 b andelectromagnet 223 from the rotor 219 and field controllable material 217substantially fills the gaps. The magnetic flux line 227 represented asdashed in FIG. 4, causes the rheology of material 217 to change therebyproducing a torque dissipating force that acts on the working surfaces219 a, 219 b of the rotor 219 to impede rotation thereof.

A fifth embodiment brake 301 is disclosed in FIG. 5 and the fifthembodiment brake is similar to the embodiment of FIG. 3.

The fifth embodiment brake comprises a housing 303 having a chamber 305for housing control means such as integrated control electronics orcontrol devices and such is identified schematically at 311. Shaft 309extends through second chamber 305 and into a first chamber 307 and therotor 315 is supported on the shaft end in the first chamber 307. Thechamber 307 is closed and sealed at the axial ends by plates 351 and371. In the fifth embodiment of the invention the rotor 315, is a“drum-style” rotor similar to the rotor illustrated in the thirdembodiment of FIG. 3. The rotor comprises a wide annular outer peripheryjoined by a relatively narrow web. The shaft 309 is supported forrotation away from the rotor by two bearings 313, which for purposes ofthe present invention are conventional “dry shaft” bearings which are asuitable alternative to the roller bearings illustrated in the previousembodiments. In this fifth embodiment of the invention, the shaft 309 issuitably supported to sustain axial loading and to prevent axialmovement of the loaded shaft. A conventional thrust bearing thrustbearing 317 of conventional construction is provided along shaft 309between rotor 315 and bearing 313 to support the axial shaft loads.

The magnetic field generator 350 is located radially outwardly from theouter periphery of the rotor 315. The field generator comprises annularpole pieces 327 that enclose an electromagnetic coil 325 which incombination with field responsive material 319 and rotor peripheryproduce an electromagnetic flux represented by flux lines 329represented as dashed in FIG. 5. As shown in FIG. 5 the field responsivematerial is located in the annular gap separating the outer periphery ofthe rotor and the field generator.

In the fifth embodiment brake 301, the plates 351 and 371 that close theaxial ends of chamber 307 comprises tapered inner walls 331 and 333respectively. As shown in FIG. 5, the walls generally taper outwardlyfrom the axis of rotation 373. In this way, the chamber narrowsprogressively as the distance from the axis decreases and, conversely,the chamber widens progressively as the distance from the axisincreases. The maximum axial dimension of the chamber occurs proximatethe rotor outer periphery and field generator 350. As a result of theforegoing chamber taper, the shear rate of the field responsive materialcan be made substantially constant or increase as the distance from theaxis increases and the axial chamber dimension decreases such thatmigration of controllable material 319 is promoted in the direction ofarrow 335 away from seals 321. The seal 321 in this embodiment can takethe shape of v-seals which provide a material-free region between anextension of the seal 321 which slides against the surface of rotor 315as it rotates, preventing material from contacting the bearing 313, inthis case dry shaft bearing 313. Other face seal and lip sealconfigurations can be used in this region. Similarly, a well structure314 as shown, creates a tortuous path tending to keep the material awayfrom the seals 321.

FIG. 6 illustrates in cross-sectional view along lines 6-6 of FigureSand represents one arrangement for connecting the shaft 309 and rotor315. As shown in FIG. 6, shaft 309 is shaped as a rectangle at theregion of the rotor 315 to fit within a mating square-shaped aperturewithin the rotor. It is possible in such a configuration to allow forrelative slippage or backlash between the shaft 309 and the rotor 315.In some cases it may be desirable to allow for such slippage orbacklash. For example, when the device with which the brake isassociated has reached its end-of-motion point and the electromagneticfield is at full strength, such slippage or backlash may be desirable toallow a relatively small movement of the shaft 309 without movement ofthe rotor being detected by a sensor of the control means which wouldtrigger a reduction of the electromagnetic field thereby allowing anoperator to move the device associated with the brake away from theend-of-motion position. In this way the device could be displaced awayfrom the end of motion position without first having to overcome thestrong material shear stress associated with being at the end of travellocation. While a square arrangement is shown, it will be appreciatedthat other configurations, such as a grooved circular cross section suchas a splined shaft and grooved engagement surfaces on the rotor,slightly mismatched in dimension, can provide a similar function, aswell as other arrangements as will be readily apparent to those ofordinary skill in the art.

As will also be readily apparent to those of ordinary skill in the art,the various features of the various embodiments can be interchanged asmay be appropriate for the particular configuration, by providing abrake in which the rotor is supported by a shaft on one side only andhaving two bearings to support the shaft, in all cases a cavity can becreated in which, in one housing can be housed various sensors, controlmeans electronics and other items that the system may require in anintegrated package.

Thus, there has been shown and described an improved brake with fieldcontrollable material. It will be apparent to those skilled in the art,however, that many changes, variations, modifications, and other usesand applications for the subject device are possible, and all suchchanges, variations, modifications, and other uses and applicationswhich do not depart from the spirit and scope of the invention aredeemed to be covered by the invention which is limited only by theclaims which follow.

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 26. A controllable brake, comprising: (a) a rotor shapedto have a working portion on its periphery which extends parallel to ashaft on which said rotor is mounted; (b) a shaft having said rotorconnected thereto in a manner to restrain relative rotationtherebetween; (c) a brake housing having a first sealed chamberrotatably housing the rotor therein, and including a magnetic fieldgenerator spaced from the rotor, and configured and positioned forgenerating a magnetic flux through a controllable magnetic fieldresponsive material in a direction perpendicular to the shaft and to theworking portion of the rotor, said brake housing having a second sealedchamber, said brake housing second sealed chamber housing a means forcontrolling and/or monitoring the operation of the brake; and (d) acontrollable magnetic field responsive material contained within saidbrake housing first sealed chamber in contact with at least the workingportion of the rotor.
 27. The controllable brake of claim 26, whereinsaid brake includes a seal between said brake housing first sealedchamber and said brake housing second sealed chamber, said sealpreventing migration of said controllable magnetic field responsivematerial from said brake housing first sealed chamber to said brakehousing second sealed chamber.
 28. The controllable brake of claim 26,further comprising a return-to-center active device in the brake housingfirst chamber to urge the rotor to return to a relative center position.29. The controllable brake of claim 26, wherein the shaft and rotor areconnected in a manner to allow a backlash between the rotor and theshaft.
 30. The controllable brake of claim 26, wherein said rotor has adrum shape with a wide outer portion at said periphery and joined by anarrow web proximate said shaft.
 31. A controllable brake, comprising:(a) a rotor manufactured from magnetically permeable material and shapedto have a working portion on its periphery which extends parallel to ashaft on which said rotor is mounted; (b) a shaft having said rotorconnected thereto at one end of the shaft in a manner to restrainrelative rotation therebetween; (c) a brake housing having a firstsealed chamber rotatably housing the rotor therein, and including amagnetic field generator spaced from the rotor, and configured andpositioned for generating a magnetic flux through a controllablemagnetic field responsive material in a direction perpendicular to theshaft and to the working portion of the rotor, and said brake housingincluding a second sealed chamber, said brake housing second sealedchamber housing a brake control electronics system for controlling andmonitoring an operation of the brake; and (d) a controllable magneticfield responsive material contained within said brake housing firstsealed chamber in contact with at least the working portion of the rotorsaid magnetic field responsive material having a rheology the rheologyof said magnetic field responsive material being affected by saidmagnetic field generator.
 32. The controllable brake of claim 31,wherein said brake includes a seal between said brake housing firstsealed chamber and said brake housing second sealed chamber said sealpreventing migration of said controllable magnetic field responsivematerial from said brake housing first sealed chamber to said brakehousing second sealed chamber.
 33. The controllable brake of claim 31,wherein said brake control electronics system housed in said brakehousing second sealed chamber includes a sensor for detecting a relativerotational position of the rotor, and a control electronic circuit forcontrol of the magnetic field generator to apply a magnetic field whosestrength is determined by the relative rotational position of the rotor.34. The controllable brake of claim 31, further comprising areturn-to-center acting device to urge the rotor to return to a relativecenter position.
 35. The controllable brake of claim 31, wherein theshaft and the rotor are connected in a manner to allow a backlashbetween the rotor and the shaft, and the brake control electronicssystem is configured for detecting movement of the shaft for causing themagnetic field generator to reduce the magnetic field in response to thedetected shaft movement.
 36. The controllable brake of claim 31, whereinthe rotor has a drum shape with a wide outer portion at said periphery.37. A controllable brake comprising: a brake housing comprising a firstsealed chamber and a second sealed chamber, a shaft, a rotor madeintegral with the shaft, the rotor having an outer periphery, said rotorbeing located in the brake housing first sealed chamber, a fieldgenerating means located in the brake housing first sealed chamberproximate the outer periphery of the rotor, a field responsive materiallocated in said brake housing first sealed chamber, said fieldresponsive material having a rheology, the rheology of said fieldresponsive material being affected by said field generating means, and ameans for controlling and/or monitoring the operation of the brake, saidmeans located in said brake housing second sealed chamber.
 38. Acontrollable brake comprising: a brake housing comprising a first sealedchamber and a second sealed chamber, said second chamber sealed fromsaid first chamber a shaft; a rotor made integral with the shaft, therotor having an outer periphery, said rotor being located in the brakehousing first sealed chamber; a magnetic field generator located in thebrake housing first sealed chamber proximate the outer periphery of therotor; a magnetic field responsive material located in said brakehousing first sealed chamber, said magnetic field responsive materialhaving a rheology, the rheology of said field responsive material beingaffected by said magnetic field generator; and a brake controlelectronics system for controlling and monitoring an operation of thebrake, said brake control electronics system housed in said brakehousing second sealed chamber.